The present invention relates to self-cleaning ovens and in particular, to a system for controlling the operation of a self-cleaning oven.
During the use of an oven of an electric or gas range, deposits will generally accumulate as a result of spills, boil overs and other unintended release of foods from their cooking containers. In order to ease the cleaning of the spillage, provision is made in some ranges, known as xe2x80x9cself-cleaningxe2x80x9d ranges, to raise the temperature of the cooking cavity well above that which would be used in cooking in order to carbonize or burn out the residue. In general, this is achieved by the selection through the range""s controls of a self-clean cycle. Initiation of this cycle typically sets a high control temperature for the range, locks the oven door at some predetermined time or temperature and proceeds to heat the cavity to a relatively high temperature for a predetermined time before ending the cycle, allowing cooling to occur and then releasing the door lock as an end to the cycle.
Typically, the time period set for this self-clean cycle is determined by the assumption of a worst case cycle. During the cycle, odors or even smoke may be released in the range environment and significant energy is used to hold the cooking cavity at a high temperature. Because of odor and smoke release, users are advised to open windows and will frequently leave the kitchen area for an extended period of time while self-clean is performed.
If a method can be devised which adjusts the time of self-cleaning to that needed for the existing degree of soil accumulation, then cycle times and their negative impact on kitchen environment and energy usage can be minimized.
U.S. Pat. No. 4,954,694 discloses a self-cleaning oven which incorporates a heat controlled unit which is responsive to a gas signal from a gas sensor located in the exhaust passage. The gas sensor measures humidity or carbon dioxide levels. The heat control samples the gas signal at a given time interval to detect a variation of amount of the gas component and detect a first inflection point from decreasing to increasing or visa versa in a gas-component variation and a second inflection point from decreasing to increasing or vice versa in the gas component variation after detection of the first inflection point. The heat control means determines the heating time period for cleaning in correspondence with the second inflection point. An oxidizing catalyst is provided in the exhaust passage, upstream of the gas sensor.
The present invention is directed to an oven capable of being operated in a self-cleaning, cycle wherein the time period of the self clean cycle is responsive to the amount of soil accumulation in the oven. The oven includes a cooking chamber, a heating device for supplying heat into the cooking chamber and an exhaust flue extending from the cooking chamber leading to atmosphere. A heat control device is provided for controlling the operation of the heating device and an input device is used for signaling the heat control device to initiate the self-cleaning cycle. A gas sensor communicates with the exhaust flue for measuring a concentration of a gas component produced from combustion of food soils within the cooking chamber. The gas sensor has a signal output indicative of the measured concentration of the gas component during the self-cleaning cycle. The heat control device receives successive gas concentration signals from the gas sensor and calculates a gas concentration versus time curve. The heat control further calculates a gas concentration area representing the area under the gas concentration curve, and terminates the self-cleaning cycle in correspondence with the gas concentration area.
The heat control device may further determine the peak gas concentration and/or the slope of the gas concentration curve for a period of time. The self clean cycle may then be terminated in response to the calculated gas concentration area and the peak gas concentration value and/or the calculated slope value.
The present invention is also directed to a method of controlling the self-cleaning of a cooking oven cavity having an exhaust flue. The method includes the step of heating the interior of the oven cavity to a pyrolyzing temperature greater than 800xc2x0 F. The concentration of a gas component produced from combustion of food soils within the oven cavity is measured by receiving successive gas concentration signals from a gas sensor communicating with the exhaust flue. A gas concentration versus time curve is calculated and a gas concentration area representing the area under the gas concentration curve is also calculated. Heating of the oven cavity is terminated after a determined time which is correlated to the gas concentration area.